Remote testing and monitoring to a cell site in a cellular communication network

ABSTRACT

Systems and methods provide remote performance monitoring and testing to a cell site in a cellular communications network. The systems and methods include a network management center having remote monitoring and testing capabilities utilizing an intelligent customer service unit that traps and makes available alarm information on the transport link.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application filed in accordance with35 U.S.C. § 119, 120 or 365, and this continuation application containssubject matter which is related to the subject matter of the followingco-pending applications, each of the below listed applications is herebyincorporated herein by reference in its entirety: application Ser. No.10/049,091, entitled “Remote Testing And Monitoring To A Cell Site In ACellular Communications Network”, which claims the benefit of PCTApplication PCT/US00/40473 filed Jul. 24, 2000 entitled “Remote TestingAnd Monitoring To A Cell Site In A Cellular Communications Network”.

BACKGROUND

Exemplary embodiments relate generally to remote testing and monitoringin a telecommunications network and, more particularly, to systems andmethods for remote testing and performance in a wireless network to acell site.

Wireless communications services have grown in popularity in recentyears. The demand for services such as paging, cellular, personalcommunications services and mobile radio has increased and customersexpect high quality, low cost service. Many telecommunications providersare transitioning from the well-established analog cellular service todigital cellular service where more features and services are possible.For example, currently the majority of wireless traffic is voice trafficbut in the near future the telecommunications companies predict thatdigital service demands will exceed requirements for voice service.

Cellular telephone networks typically involve numerous service providersand equipment. For instance, a local telephone company may manage theservice from a cell site to a switch where a long distance providerswitches the call throughout its network to call completion.Alternatively, one company can provide end-to-end service. Or acombination occurs where a local company takes the call from the cellsite to locations within its local territory and to a long distanceprovider who switches the call across the country. Potentially, amultitude of service providers can be involved as voice and datacommunications traffic travels from end to end. As the number ofproviders increases, sources of potential problems grow requiringeffective, efficient trouble isolation for problem resolution.

While the reliability of wireless communications networks has increased,often cell sites stop working. Determining where the problems reside ischallenging because communications networks include numerous components,such as, cell site equipment, central office equipment, and facilities,all which can be provided by different service providers.

One method for clearing troubles is to utilize a central networkmanagement center with remote access to certain portions of the network.The network management center checks a portion of the network. Eitherthe network management center personnel clear the trouble remotely orthey dispatch a technician to the troubled location to clear theproblem. Technicians provide hands on support for both installation andmaintenance of the communications network. The technician must drive tothe cell site location, determine the problem and correct the problem.To determine what portion of the network is in trouble, the technicianmust eliminate a multitude of problems, for instance, a down telephonelink to the cell site, broken cell site equipment, damage to the cellsite caused by lightening, or conclude that the problem is somewhereelse in the network. Cell sites can be geographically dispersed, perhapsremotely located, such as in a wooded area, requiring a technician todrive several hours just to reach the cell site. Thus, isolating aproblem is a long arduous process.

In the current environment, historical performance data of the transportlink to the cell site can be provided, however, real time informationcannot be provided. Thus, a technician may arrive at the troublelocation only to find that no trouble exists because, for instance, thetrouble became clear in the time it took for the technician to arrive,the problem was not isolated to the correct piece of equipment, or thefacility works properly from the technician's location towards thecentral office and the problem exists in a another portion of thenetwork.

Solving these problems requires coordination among numerous peopleincluding: local carriers, long distance carriers, independent carriers,and equipment vendors. One call could involve as many as forty differentcarriers, making coordination between carriers a time consuming andchallenging task.

Customer satisfaction suffers when technicians or network managementcenter personnel cannot correctly identify the problem or when theproblem cannot be timely resolved due to coordination problems among thevarious suppliers.

Customer satisfaction also suffers when the problem “came clear” sincethe customer may not be satisfied that the problem will not occur again.Solving problems is exacerbated when a cellular network containsthousands of cell sites, each of which could at some point have troublerequiring technician dispatch to resolve.

Several types of wireless communications services exist, such as theNorth American Global System for Mobile Communications (GSM) cellularcommunications networks, code division multiple access (CDMA) and timedivision multiple access (TDMA) networks. Each network typicallyincludes a cell site having a tower and associated equipment, a customerservice unit (CSU), transport links, central office equipment, andfacilities connecting the transport link to a switch. Currently, centraloffice or network management center personnel cannot remotely test thetransport link in real time all the way to the cell site. Most failuresin a cellular network occur between the transport links connecting thecell site to the switch, where real time remote testing is unavailable.Only historical (e. g., past) data on a circuit performance isavailable.

Thus, no effective real time system or method exists for remote testingor performance monitoring of the transport links connecting cellularsites to a switch.

Remote testing personnel and other maintenance personnel cannot “see”what is happening beyond channels in a digital access and cross connectsystem (DACS) in the central office. If the location where the troubleoccurred cannot be identified, repairing the problem is morechallenging. Thus, preventative testing or performance monitoring of anytransport links must be performed by local field technicians utilizingperformance reports with only historical data derived from an operationsmanagement center. The operations management center using the historicaldata produce historical transmission statistics that then can bereviewed manually to gain some insight into the health of the transportlinks. Resource and technological constraints currently prevent anyeffective proactive, real time circuit monitoring and maintenance.

As the cellular transport network becomes larger and more complex,insuring transport link quality becomes a greater challenge. Without thecapability of robust remote testing, monitoring and analytical systems,the network is subject to less than optimal transport link quality, agreater number of field technicians are needed to handle transport linkproblems, and transport link maintenance suffers as a result of fieldtechnicians working priority outages.

Due to bandwidth limitations and limitations in the existing CSU,network performance monitoring has not reached the cell site. As aresult, existing network monitoring configurations stop at the transporthub where some piece of edge transmission equipment resides.

Thus, this disclosure addresses the problems in the prior art andprovides systems and methods for remote testing and performancemonitoring of a cellular communications network that brings transmissionsurveillance to the cell site.

BRIEF SUMMARY

Exemplary embodiments include systems and methods for providing remoteperformance monitoring and testing to a cell site in a cellularcommunications network. The systems and methods include a networkmanagement center having remote monitoring and testing capabilitiesutilizing an intelligent customer service unit at the cell site andworking in cooperation with a communication link having a spare channelfor use as a management channel. The network management center hasmonitoring and testing capabilities for remotely accessing themanagement channel. The intelligent CSU captures information on themanagement channel and sends an alarm when quality thresholds are notmet.

Moreover, network management personnel can poll the intelligent CSU togain real time performance information on the management channel. Thus,the features of this disclosure include the following:

To provide a system that improves productivity for network personnel byeliminating the guesswork in finding and isolating network problems,thus reducing unnecessary dispatch of technicians and reducing the meantime to repair.

To provide a system that improves productivity for a network managementcenter by allowing technicians to instantly focus on resolving networkproblems rather than deciphering the network configuration.

To provide a system that reduces overtime call outs by enabling thenetwork management center to remotely perform network testing andmonitoring.

To provide a system that reduces the number of network outages bypredicting, identifying and fixing network problems before they occurthereby improving customer satisfaction.

To provide a system and method that improves network quality byproviding a remote, non-intrusive method of identifying and isolatingintermittent problems.

To provide a tool for tracking continued improvement initiatives withsuppliers by allowing a comparison of supplier network performance,supplier trend analysis, and identifying suppliers' worst circuitsegments.

Other features of this disclosure will be set forth in part in thedescription which follows and in part will be obvious from thedescription or may be learned by practice of the exemplary embodimentsin this disclosure. The features of this disclosure will be realized andattained by means of the elements and combinations particularly pointedout in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a traditional cellular communications network withoutcapabilities for testing and monitoring transport links to the cellsite.

FIG. 2 shows a flow diagram of a cellular communications network havingcapabilities to remotely test and monitor transport links through thenetwork to the cell site according to exemplary embodiments.

FIG. 3 shows a flow chart of the main processes performed by theintelligent CSU according to exemplary embodiments.

FIG. 4 shows an alternative embodiment of a system for remotely testingand monitoring transport links to a cell site.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Reference will now be made in detail to exemplary embodiments, examplesof which are illustrated in the accompanying drawings.

FIG. 1 shows a traditional cellular communications network 100. Thecellular communications network 100 includes switches 102 thatcommunicate with other switches located throughout the communicationsnetwork 100, and a hub 104 having equipment adapted to communicate withthe switch 102. Multiple switches 102 and hubs 104 exist throughout thenetwork. A variety of network providers, such as, local telephonecompanies, long distance telephone companies and independent telephonecompanies can supply parts of the cellular network. A digital service,level 3 (DS3), also referred to as a T3, outputs 106 from the hub 104and provides 28 1.544 Mbps circuits. A local network 107 translates theDS3 to a digital service, level 1 (DS1) channel 108 of 1.544 Mbps. TheDS1 channel 108 couples to a Network Interface Unit (NIU) 110. The NIU110 is positioned between the local network 107 and a cell site 112 orcustomer premise. The NIU 110 serves to interface and isolate thenetwork from cell site equipment 114. The DS1 channel 108 enters aCustomer Service Unit (CSU) 116. The CSU 116 is located in a cabinet atthe cell site 112 along with associated cell site equipment 114. A tower118 receives communications from and passes detected communications tothe cell site equipment 114 and CSU 116. CSUs 116 are prescribed by theFederal Communications Commission (FCC) and serve several functions. TheCSU 116 is an interface point for the local telephone company (Telco)and isolates Telco equipment from the network carrier's equipment. Byproviding electrical isolation from the carrier's circuit, the CSU 116functions similar to a surge protector. CSUs 116 also provide bitstuffing to ensure synchronization and ones density. Additionally, CSUs116 provide signal amplification when necessary and keeps some signalsalive if the network goes down.

Traditionally, cellular communications networks cannot efficiently,effectively and in real time provide remote testing and monitoring tothe cell site.

Real time remote testing in the cellular communications network of FIG.1 stops at the NIU 110, shown as line A-A in FIG. 1. Historical networkperformance data can be obtained by hub 104 personnel who later performanalysis and trending of the data.

FIG. 2 shows a diagram of a cellular communications network 200 havingcapabilities to remotely test and monitor the transport links to a cellsite according to exemplary embodiments. The network 200 includes aswitch 202, a hub 204 including a network management center 206, a landnetwork which can be a BellSouth land network (BST land) 208, a NIU 210,a cell site cabinet 212 enclosing an intelligent CSU 214 and cell siteequipment 216, and a tower 218. An intelligent CSU 214 manufactured byADC Kentrox of Portland, Oreg. on behalf of BellSouth CellularCorporation is suitable for this disclosure. For simplicity, only oneswitch 202 is shown, however, multiple switches handling many calls canbe switched through the hub 204. The switch 202 connects the callthrough the network 200, and potentially other networks to the calleddestination.

A digital access and cross-connect system (DACS) 220 serves to route andswitch digital service lines including DS1 and DS0 lines among multipleTi ports of the DACS 220. Calls from the switch 202 enter the hub 204and eventually couple to the DACS 220. The DACS 220 serves more as amultiplexer than a switch. Traditional network supervision stops at theswitch 202 side of the DACS 220. Network supervision involves detectingwhen calls complete and terminate so that billing can be determined.While the DACS 220 has quality indicators and can be polled, the DACS220 cannot establish software traps to capture network performance databased upon quality thresholds.

The NMC 206 has capabilities to access the DACS 220 to test and monitorchannels from the DACS 220 looking towards the cell site and lookingtowards the switch 202. A test head 222 coupled to the DACS 220 performsremote Ti testing utilizing remote testing software. TTH Corporation ofGermantown, Md. makes a test head model 650S that is suitable for thisdisclosure.

The cellular communications network may be a North American GlobalSystem for Mobile Communications (GSM) network. However, TDMA and CDMAnetworks are encompassed by exemplary embodiments and provide networkscompatible with features of exemplary embodiments. The North AmericanGSM network topology contains spare bandwidth that is utilized in thisdisclosure. The GSM configuration leaves several timeslots, (i.e., sparebandwidth) vacant that can allow for surveillance all the way to thecell site. For instance, up to three spare DS0 channels 226 per DS1channel 209 are available. Thus, because the GSM communications networkleaves several time slots vacate to the cell site utilizing anintelligent CSU 214 at the cell site, the disclosure extends networksupervision to the cell site, allowing remote performance monitoring.Further, utilizing the intelligent CSU 214 in cooperation with DACS 220provides for intercepting the spare bandwidth and utilizing it fortesting and monitoring purposes.

Exemplary embodiments utilize the spare DS0 channels 226 and configurethe intelligent CSU 214 to use the spare DS0 channels 226 for networkperformance testing and monitoring. Both the DS1 209 and DS0 226channels are in communication with the intelligent CSU 214. DS3 channels224 and the spare DS0 channels 226 from the DACS 220 couple to the BSTland 208 network.

Customer traffic is on the DS1 channel 209. The spare DS0 channels 226are utilized to return alarms from the intelligent CSU 214 back to thehub 204 without interrupting customer traffic on the DS1 channel 209.Thus the DS0 channel 226 is also referred to as the management channel.The intelligent CSU 214 communicates alarm data over the managementchannel 226. In one embodiment, the BST land 208 is a wireline networkfrom the hub 204 to the NIU 210. The NIU 210 serves to protect the cellsite and customer equipment from big surges by isolating the customerequipment and cell site from the network. An output of the BST land 208is DS1 channels 209 and the spare DS0 channels 226. Because one DS3channel 224 equates to three DS1 channels 209, other DS1 channels 209and DS0 channels 226 from their associated NIUs interface and cell sitescouple to the BST land 208 and connect to the hub 204. Each cell sitemust be customized so that the cell site equipment 216 and hub equipment204 are configured to recognize which of the three spare DS0 channels226 among the three spare DS0 channels 226 is utilized as the managementchannel. The test head 222 coupled to the DACS 220 allows NMC personnelto test a circuit, i.e., the DS0 channel 226, made available by the DACS220.

The intelligent CSU 214 of this disclosure provides all of thecapabilities of the CSU 116 of FIG. 1, plus provides remote transmissionmonitoring and testing. The intelligent CSU 214 includes an Internetprotocol (IP) software trap that provides an immediate warning of signaldegradation without waiting on a polling cycle. A number of qualityindicators alert NMC personnel to potential network problems. A sampleof quality indicators that can be monitored includes: severe erroredseconds (SES), errored seconds (ES), alarm indication signal (AIS),yellow alarms, extended super frame errors, out of frame errors, loss offrame errors, loss of signal errors, slip errors, cyclic redundancycheck (CRC) and bipolar violations. Thresholds for each qualityindicator can be set and trapped by the intelligent CSU 214. Thesethresholds also include timing characteristics for measuring errors anddeactivation of alarms.

The intelligent CSU 214 contains configurable alarms that trigger whencertain thresholds are met. Alarms can be triggered by an erroroccurrence on the input signal. Cell site equipment configures to matcha data port configuration of the intelligent CSU 214. When an out ofrange occurrence transpires, the intelligent CSU 214 alarms and outputsthe trapped data. The IP traps utilize a TCP/IP network by requiring adestination IP address for sending the trapped data.

The IP address is typically a 32-bit address, used in IP routing whichincludes a network portion and a host portion. The data transmits overthe management channel to the destination IP address. Alarms allow theNMC personnel to monitor the management channel for errors and takecorrective action. This feature prevents interruption or deteriorationof a customer's service since problems can be corrected prior to acustomer's service being affected. The intelligent CSU 214 collectserror messages and sends a message back through the network to the NMCpersonnel who take appropriate action. If the condition that triggeredthe alarm goes away the thresholds are reset. Optionally, networkmanagement personnel remotely reset threshold levels.

NMC personnel gain access to the real-time data of the intelligent CSU214 via Telnet. Telnet is a TCP/IP protocol having terminal emulationthat allows remote connections to other computers. Thus. NMC personnelcan access the intelligent CSU 214 utilizing Telnet and work from theNMC as if their terminals were directly connected to the intelligent CSU214. The intelligent CSU 214 configures to operate with the TCP/IPnetworks utilizing the IP address for the network. This arrangementprovides the NMC personnel real time access to the management channel226, performance data and alarm data.

For instance, once a quality threshold has been crossed, NMC personneltest the DS0 channel 226 in real time, or poll the intelligent CSU 214for the last 24 hours worth of data for analysis and trending.Historical and real time statistics can be compiled utilizing theintelligent CSU 214. NMC personnel can perform loop back tests utilizingthe intelligent CSU 214. Loop back tests involve testing a line bysending a signal to a remote piece of equipment and analyzing thereturned signal for errors. With the intelligent CSU 214, NMC personnelcan use the management channel 226 to perform loop back tests withoutinterfering with a customer's service. Further the data can indicatethat the cell site is not receiving the circuit properly from anothercarrier and so that carrier is called. Thus, exemplary embodimentsprovide a diagnostic tool that reduces trouble isolation time.

Moreover, the intelligent CSU 214 provides endpoint visibility and givesthe system supervision and testability through an entire drop and insertchain. The drop and insert chain includes locations where a portion of achannel such as data of a DS1 or T1, are “dropped off” to a digitaldevice. The multiplexing device then “stuffs” bits into the channelsdropped off to the data devices and sends a complete or full T1including the bit stuffed channels to the multiplexing equipment.Further the intelligent CSU 214 contains a polling algorithm allowingpolling of the spare DS0 channel 226 performance indicators. ClearCommunications of Lincolnshire, Ill. provides software called Clearviewsuitable for polling the network. The real time reporting capability ofthe exemplary embodiments reduces the necessity of polling. However, theoption of polling exists.

Currently, most traffic sent over a cellular network is voice traffic.Over time, data traffic will become more prevalent. Frame relayswitching techniques provide one mode of managing data traffic. Framerelay is a network shared by multiple users, built by local and longdistance network providers that performs like a private network. Framerelay networks can switch small packets of bursty data over a wide areanetwork. A data link connection identifier (DLCI) provides a destinationfor alarm data trapped by the intelligent CSU 214 sent out of a framerelay network. Traffic transported utilizing frame relay and othernetwork equipment located in the hubs 204, couples to access lines thatprovide access from a user's equipment, such as cell site equipment, tothe frame relay network.

Access lines can be T1 or T3, for instance, and thus can be switchedthrough a DACS 220. At this point, the traffic can be transportedthrough to the cell site where the traffic can be monitored by theintelligent CSU 214.

Alternatively, an Asynchronous Transfer Mode (ATM) system switches thetraffic. ATM provides for high speed, high bandwidth, packet typeswitching and multiplexing of traffic, including data, voice, video andmultimedia images.

ATM's switch data in discrete cells that are fixed in size, andasynchronously switched in hardware. However, an ATM system can bescaled down to speeds of 56 kbps and thus, DS3, DS1 and DS0 traffic canbe switched through the DACS 220 through the network to a cell site.Performance monitoring and testing are possible using the intelligentCSU 214 and DS0 circuit of an ATM. Framing formats configure to matchthe framing format for the intelligent CSU 214.

Quality indicators such as frame bit errors threshold levels are set inthe intelligent CSU 214. The thresholds for ATM quality indicators canbe set to measure for instance, the number of packets discarded and thenumber of packets delayed.

FIG. 3 shows a flow chart of processes performed by the intelligent CSUaccording to exemplary embodiments. At 240, the intelligent CSU 214recognizes that the signal on the management channel 226 does not meetthe quality thresholds established by the quality indicators. At 242,the intelligent CSU 214 recognizes that an alarm state has occurred. Theintelligent CSU 214 generates an alarm, at 244. At 246, a counter in thememory of the intelligent CSU 214 counts each signal condition that doesnot meet threshold levels for the duration of the alarm state or untilthe alarm state is deactivated. Updating and displaying the statusinformation and signal condition occurs at 248 and this information isplaced at the data port and interfaces to cell site equipment, and thenetwork interface. At 250, the IP trap data is output and transmittedout of data ports and interfaces at 252. At 254 the intelligent CSU isreset based on pre-determined criteria or as a result of externalintervention, for instance reset by NMC personnel.

FIG. 4 shows another alternative embodiment of a network 300 forproviding remote personnel access to a cell site. In an alternativeembodiment where no spare DS0 channels exist, remote testing andmonitoring is providing utilizing a spare data port of the intelligentCSU 214. A wireless transceiver, such as a modem, 215 is added at thecell site and adapted to communicate with the spare data port 217.Remote personnel such as NMC personnel can call the cell site towerusing the wireless transceiver 215. This arrangement allows the remotepersonnel to access the CSU to “look” at the circuit from the cell sitethrough the network. A tower 320 is placed on a hub. Another tower 322is placed between the BST land 208 and the intelligent CSU 214. A DS1channel 209 or management channels from the hub 304 come into theintelligent CSU 214 bringing the alarms. A wireless transceiver 215 incommunication with a data port 217 in the intelligent CSU 214communicates performance data to the tower 322.

The towers 320 and 322 are utilized to send the signals back over themanagement channel 209 when remote personnel perform testing loop backs.The loop backs are performed without interrupting customer service onthe land based DS1. This network 300 is more costly and less efficientthan network 200 due to the required towers 320, 322 and equipment, andbecause this embodiment utilizes a DS1 channel 209 instead of a DS0channel 226 as the management channel.

A feature of this disclosure is that it provides remote personnelcapabilities to remotely test transport links to a cell site utilizingan intelligent CSU. By some estimates, ninety percent of failures in awireless network occur between the BST land and the CSU and only tenpercent occur between the hub and the switch. Thus, providing adiagnostic tool giving access and monitoring capabilities to the NMCpersonnel through to the CSU can drastically improve transport linkperformance.

Another feature of this disclosure is that the NMC personnel can isolatenetwork troubles without the aid of field personnel.

Still another feature of this disclosure is that the NMC personnel canmonitor and test any circuit for any reason without interrupting acustomer service.

Yet another feature of this disclosure is that the NMC personnel havemeans to prevent some outages as degrading circuits are brought to theirattention by this disclosure.

The forgoing description of the exemplary embodiments of the disclosurehave been presented only for the purpose of illustration and descriptionand is not intended to be exhaustive or to limit the disclosure to theprecise forms disclosed.

Many modifications and variations are possible in light of the aboveteaching.

The embodiments were chosen and described in order to explain principlesand their practical application so as to enable others skilled in theart to utilize the disclosure and various embodiments and with variousmodifications as are suited to the particular use contemplated.

1. A method, by an intelligent customer service unit (CSU), for remotelymonitoring a transport link operatively connecting a switch and a cellsite, the method comprising: gathering performance data of a transportlink; recognizing which of a plurality of spare digital signal zero(DS0) channels is a DS0 management channel, the plurality of spare DS0channels coupling a network management center and a cell site; andsending a message, to the network management center, as a managementsignal responsive to the performance data of the transport link notmeeting a quality indicator.
 2. The method of claim 1, furthercomprising receiving test signals on the DS0 management channel todiagnose the transport link not meeting the quality indicator.
 3. Themethod of claim 1, wherein sending the message comprises transmitting atrap to the network management center.
 4. The method of claim 1, whereinsending the message to the network management center comprises sendingthe message on the DS0 management channel.
 5. The method of claim 1,wherein a customer service unit (CSU) recognizes the DS0 managementchannel.
 6. The method of claim 1, further comprising responsive to thenetwork management center recognizing the DS0 management channel andresponsive to a customer service unit (CSU) recognizing the DS0management channel, receiving a request for the performance data.
 7. Asystem configured to remotely monitor a transport link operativelyconnecting a switch and a cell site comprising: a customer service unit(CSU) configured to obtain performance data of a transport link; thetransport link having a plurality of spare digital signal zero (DS0)channels; the customer service unit configured to recognize which of theplurality of spare digital signal zero (DS0) channels is a DS0management channel, the plurality of spare DS0 channels coupling anetwork management center and a cell site; and the customer service unitconfigured to communicate with the network management center on the DS0management channel.
 8. The system of claim 7, wherein the customerservice unit is configured to send a message to the network managementcenter on the DS0 management channel responsive to the performance dataof the transport link not meeting a quality indicator.
 9. The system ofclaim 8, wherein the message indicates that the performance data of thetransport link does not meet a quality indicator.
 10. The system ofclaim 7, wherein the customer service unit is configured to receive testsignals from the network management center on the DS0 managementchannel.
 11. The system of claim 8, wherein the message is a trapcomprising the performance data.
 12. A system configured to remotelymonitor a transport link operatively connecting a switch and a cell sitecomprising: a network management center configured to receiveperformance data of a transport link from a customer service unit; thetransport link having a plurality of spare digital signal zero (DS0)channels; the network management center configured to recognize which ofthe plurality of spare digital signal zero (DS0) channels is a DS0management channel, the plurality of spare DS0 channels coupling thenetwork management center and a cell site; and the network managementcenter configured to communicate with the customer service unit on theDS0 management channel.
 13. The system of claim 12, wherein the networkmanagement center is configured to receive a message on the DS0management channel from the customer service unit.
 14. The system ofclaim 13, wherein the message is received by the network managementcenter responsive to the performance data of the transport link notmeeting a quality indicator.
 15. The system of claim 13, wherein themessage indicates that the performance data of the transport link doesnot meet a quality indicator.
 16. The system of claim 12, wherein thenetwork management center is configured to send test signals on the DS0management channel to the customer service unit.